Show HN: APC Playground – Stop AI agents from modifying your API tool calls

APC Playground is a browser-based lab for writing policy expressions in a restricted grammar (policy.apc) that evaluate API tool calls, with a local runtime and no network requests. It shows evaluation results, checks, and an exportable evidence record, and notes that the evidence digest is a content-integrity checksum rather than a signature or attestation, and that the lab does not establish production enforcement.